Voltage source converter

1. An apparatus for controlling a voltage source converter with at least two bridges of semiconducting self commutating elements connected in anti-parallel with a diode, the apparatus comprising:

means for producing a switching control pulse train to form a fundamental frequency,

means for effecting a switching order and means for detecting a switching event,

computer means for calculating a reaction time between a switching order and a switching event for a selected pulse of the pulse train, and

means for adaptively adjusting the switch order of an equivalent pulse in a subsequent period of a harmonic period of the fundamental frequency utilizing the calculated reaction time.

2. The apparatus according to claim 1 , wherein the means for adaptively compensating the switch order comprises a memory means for storing the calculated reaction times of each pulse of the harmonic period of the fundamental frequency.

3. The apparatus according to claim 1 , wherein the means for detecting a switching event comprises means for measuring a voltage across electrodes of at least one semiconductor device in a valve.

4. The apparatus according to claim 1 , wherein the means for producing a switching control pulse train comprises an optimum pulse width modulator.

5. The apparatus according to claim 1 , wherein the computer means for calculating a reaction time comprises means for calculating a mean value for the reaction time of each pulse in the harmonic period of the fundamental frequency.

6. The apparatus according to claim 5 , wherein the mean value comprises an exponential mean value.

7. A method for controlling a voltage source converter comprising at least two bridges including semiconducting self commutating elements, each connected in anti-parallel with a diode, and a control equipment, the method comprising:

arranging a pulse train for forming a fundamental frequency, defining an instant to send a switching order of a pulse of the pulse train of the fundamental frequency,

sending the switching order,

determining the actual switching event,

comparing the actual switching event with a desired switching event, and

adjusting the instant to send the switching order of an equivalent pulse in a next harmonic period of the fundamental frequency based upon the comparing of the actual switching event and the ideal switching event.

8. The method according to claim 7 , wherein the determination of the actual switching event comprises measurement of a voltage across electrodes of at least one of the semiconducting elements.

9. The method according to claim 7 , wherein adjusting the instant to send the switching order of the equivalent pulse in the next harmonic period comprises a blanking time adjustment.

10. A method for controlling a voltage source converter by a pulse width modulation pulse signal comprising an ideal switching instant for each switching pulse, the method comprising:

detecting an actual switching event for a selected switching pulse in a first period of a fundamental frequency,

adjusting an action time for the selected switching pulse by comparison of the ideal switching instant and the actual switching event, and

correcting a switching order of a corresponding pulse in a following period of the fundamental frequency utilizing the adjusted action time.

11. A computer program product, comprising:

a computer readable medium; and

computer program instructions recorded on the computer readable medium and executable by a processor for performing a method comprising arranging a pulse train for forming a fundamental frequency, defining an instant to send a switching order of a pulse of the pulse train of the fundamental frequency, sending the switching order, determining the actual switching event, comparing the actual switching event with a desired switching event, and adjusting the instant to send the switching order of an equivalent pulse in a next harmonic period of the fundamental frequency based upon the comparing of the actual switching event and the ideal switching event.

12. The computer program product according to claim 11 , wherein the method further comprises providing the computer program instructions at least in part over a network.

13. The computer program product according to claim 11 , wherein the method further comprises providing the computer program instructions at least in part over the Internet.